The present invention relates to an apparatus for detecting in-band single frequency signaling tones from frequency-division multiplexed channels or detecting digital in-band single frequency signaling tones from time-division multiplexed channels of a telecommunication system.
In frequency-division multiplexed communication systems employing in-band single frequency signaling tones, detection of the tone signals currently involves the use of a plurality of signal converters of analog circuitry provided one for each of the multiplexed channels which separate the single-frequency signaling tones from speech signals. One disadvantage of the current practice is that the number of signal converters and hence the total equipment cost and size increase as a function of the number of channels.